Yeast, Eukaryote, Mitochondria, Dna, Rna, Phenotype, Species

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Lab Report
Abstract
Yeast, with its single-celled growth habit, is easy to be contrasted with molds that grow hyphae. Fermentation is the process in which the yeast species Saccharomyces cerevisiae becomes able to convert carbohydrates to alcohol and carbon dioxide. For hundreds of years, carbon dioxide is being extensively used in baking and alcohol is used in preparing beverages of different types, varieties, qualities and tastes. In this lab project, a series of petite mutants of Saccharomyces cerevisiae was isolated and generated after treating with ethidium bromide for multiple times. It should be noticed that the petite is caused by the deficiency of cytochromes (such as a, a3 + b) and due to the lack of respiratory enzymes that are involved in the mitochondrial respiration. Yeast is unable to grow on a media that contains only non-fermentable carbon sources because of the possibility of errors in the respiratory chain pathway. It means ethanol and glycerol may not be suitable for lab projects like this. In the absence of mitochondria, the petite phenotype could be cause or mutation in mitochondrial DNA may take place, which is actually a deletion mutation. Another case is the mutation of nuclear-encoded genes that involve oxidative phosphorylation (Stewart 309).
Keywords: yeast, eukaryote, mitochondria, DNA, RNA, phenotype, species, organisms, unicellular, multi-cellular
Introduction
Yeast is eukaryote, single-celled microorganism. It is considered an active member of the fungus kingdom. As of now, over 1400 species of yeast have been identified, and they constitute only 1 percent of the total fungal species, some of which have been identified and some are still unidentified. Yeasts are said to have been evolved from multi-cellular organisms, and some of the species of yeasts possess characteristics similar to that of their ancestors, with an ability to form multiple strings of budding cells known as false hyphae or pseudohyphae (Schneider-Berlin et al. 91). When it comes to talking about the size of yeasts, we should notice that their sizes differ from species to species and mainly depend on the environment they live in and the availability of food. Typically, their measurement is 3 to 6 µm in diameter, and some yeasts can grow up to 40 µm in size. All species of yeasts are capable of reproducing asexually through a process known as mitosis, and a few of them can divide themselves through an asymmetric process called budding. Yeast is widely used for experimental purposes and can be mutated in a variety of ways. In the field of Biology, mutation is considered one of those very few processes that help experts determine the causes or biochemistry of different genetic diseases. As of now, different types of cancer cells have been studied for their shapes, sizes and the way they grow in the human body. It’s safe to say that cancer is caused by mutation, so as fragile X syndrome and Huntington’s disease. Petite (ρ–) can be regarded as a mutant discovered in the yeast Saccharomyces cerevisiae. Because of a significant defect in the respiratory chain, it is not possible for yeast to grow on a media that contains ethanol or carbon (non-fermentable carbon sources). It means yeast can grow when a sufficient number of fermentable carbon sources are available, such as glucose. It should be noticed that a petite phenotype is caused due to the absence of mitochondrial DNA (also known as cytoplasmic petite), or because of the mutation of nuclear-encoded genes involved in a biochemical reaction (oxidative phosphorylation). It is possible for us to induce petite mutation with DNA intercalating agents and chemicals that interfere with the synthesis of DNA in growing cells.
Materials & Method
Materials
1 Culture of CTY10-5d yeast
2 YPD medium
3 2 ml of aliquots of the yeast culture
4 Extra culture tubes with 3 ml of sterile YPF
5 Stock EtBr
Method
1 In the first step, an overnight culture of CTY10-5d yeast in YPD medium was grown for the class. The CTY10-5d strain of S. cerevisiae was found to be deficient in a gene of the adenine biosynthetic pathway. They were able to grow slowly due to the absence of supplemental adenine and developed a red pigmentation. In contrast, the true wild-type S. cerevisiae is likely to grow at a fast speed in the absence of supplemental adenine.
2 In the next step, about 2 ml of aliquots of the yeast culture was provided to every group so that this could be used wise...